It has long been necessary with industrial equipment such as center pivot gantry cranes to provide a track-guided wheel truck to support the outer end of the gantry beam. The wheel truck conventionally has steel wheels which ride a raised track as the truck moves in a circular path while supporting the gantry beam in its operational travel.
The track is employed to keep the truck in its proper path beneath the arcuate path of the beam end. If the truck moves or tends to move from this path, particularly while the crane is carrying a load, the beam support structure and truck are subjected to substantial stress.
As an alternative to the track guided wheel construction solution it has been demonstrated that the use of castered wheels fore and aft of a wheel truck will permit the truck to follow the beam end through its arcuate path. However, the reversal of castered wheels each time the crane reverses direction is, at least momentarily, destabilizing. It can result in high stresses being developed in the crane and truck. Furthermore, it is recognized that castered wheels, particularly in such a high load environment, have a tendency to function improperly and not reverse correctly time after time, thus engendering equipment breakdown.